1. Field of the Invention
The present invention relates to intermediate electrical connectors.
2. Related Art
An intermediate electrical connector is used to connect two circuit broads or corresponding circuit portions of connection objects. The intermediate electrical connector comprises a support plate of dielectric material and a conductive member extending through the support member. The conductive member is a molding of a conductive elastomer or a mixture of elastic polymeric material and conductive powder.
FIG. 1 shows an example which comprises a support member 51 of dielectric material and a conductive member 52 with upper and lower conic surfaces 52A attached thereto by integral molding. The upper and lower flat end faces 53 and 54 make elastic contact with the circuit portions of connection objects. The number of conductive members 52 provided on the support member 51 corresponds to the number of circuit portions of the connection objects.
In FIG. 2, two connection objects or circuit boards 55 and 56 are provided on both sides of the support member 51. The circuit boards 55 and 56 have circuit portions 55A and 56B which are pressed against the contact faces 53 and 54, compressing the conductive member 52. Thus, the two circuit portions 55A and 56B of the circuit boards 55 and 56 are connected to the conductive member 52 and short-circuited via the conductive member 52.
However, the above conventional intermediate electrical connector provides no satisfactory amount of elastic deformation of the conductive member 52. Since the conductive member 52 increases in diameter from the upper and lower contact faces 53 and 54 to the support member 51 and held by the edges of the support aperture 51A, not only the pressure upon the contact face 53 is distributed to the whole body but also a tension is produced on the conic surface 52 between the flange portion 52B and the contact face 53 of the conductive member 52, providing no satisfactory amount of deformation.
When a number of conductive members are molded with a support member, there are variations in their heights. In addition, the circuit boards and the support member are warped so that more variations are added to the conductive members. Moreover, when the intermediate electrical connector receives an external force, the circuit boards momentarily moves in the compression direction of the conductive member, causing poor contact of the conductive member. Consequently, it is necessary for the conductive member to provide a sufficient amount of deformation to absorb the above variations. However, the above conventional connector provides no satisfactory amount of deformation, thus causing poor contact.
The conductive elastomer has such a tendency that when compressed, its resistivity in the compression direction decreases. However, the amount of elastic deformation is so small that the contact resistance is high.
When it is compressed, the conductive elastomer decreases in electrical resistance at the initial stage but increases in electrical resistance beyond the initial stage. Thus, when it is compressed beyond the initial compression stage, the electrical characteristics deteriorates even though the mechanical contact is improved. In addition, if this high compression is applied to a number of conductive members, the combined force applied to the mating circuit boards is disadvantageously high.
When a number of conductive members are molded with a support member, their heights are not equal. In addition, the circuit boards and the support member are warped to worsen the variations in the contact points of the conductive members. Moreover, when the intermediate electrical connector receives an external force, the circuit boards are moved in the compression direction of the conductive member, causing poor contact of the conductive member. Consequently, it is necessary for the conductive member to have sufficient elasticity to absorb the above variations. However, too much elasticity causes lower electrical characteristics described above.